Port e18390cfe6 to glitch-soc

Port dfbadd6837 to glitch-soc

Port 023fe5181b to glitch-soc

- Move componentWillMount and componentWillReceiveProps logic to
  getDerivedStateFromProps.
- Compute CW auto-unfold status earlier

Fixes #832

Port f978afa487 to glitch-soc

Port 3cecf3e5b9 to glitch-soc

Port dd00cd19d2 to glitch-soc

Port bb5558de62 to glitch-soc

Port 9c38c5daa3 to glitch-soc

Port 795f0107d2 to glitch-soc

Port 7861c5f108 to glitch-soc

Port bebe8ec887 to glitch-soc

Fixes #780

Port 28401962ca to glitch-soc

Media modals push an history state so that pressing back on mobile closes them.
We made sure to not scroll when opening them, but not when *closing* them,
which caused some issues in rare cases.

Inspired by b79ab15859

Port f7a6f9489d to glitch-soc

[API] [vanilla required] [glitch-soc optional] initial_state show_sensitive_media boolean changed to show_media string with options "default", "hide_all", "show_all"

Fixes #751

Port 05f90e3695 to glitch-soc

Port front-end changes from f4d549d300 to glitch-soc

Port some parts from 1a7a74ff76

Port front-end changes from f8b54d229f